Pellicle frame and pellicle

ABSTRACT

The present invention provides; a pellicle frame which can effectively inhibit distortion of the photo mask ( 8 ) caused by mounting the pellicle ( 1 ), and which does not have a complex shape, and a pellicle which uses said pellicle frame are provided, and a manufacturing method of a blackened pellicle frame is also provided which can reduce the defect of the surface flickering under concentrated light and which facilitates inspection of the foreign matter adhesion prior to use. The present invention relates to a pellicle frame with an anodized film on a surface of an aluminum alloy frame, characterized in that: the aluminum alloy frame comprises an aluminum alloy which contains Ca: 5.0 to 10.0% by mass with the remainder aluminum and unavoidable impurities are contained, and has an area (volume) ratio of an Al 4 Ca phase, which is a dispersed phase, is greater than or equal to 25%, and a crystal structure of a part of the Al 4 Ca phase is monoclinic; wherein the Al 4 Ca phase dispersed in the anodized film is anodized, and the anodized film is stained with a black dye.

FIELD OF THE INVENTION

The present invention relates to a frame used for a pellicle of alithography mask used for manufacturing a liquid crystal display panelfor manufacturing a semiconductor device such as an LSI and a liquidcrystal display panel, more specifically, relates to a pellicle framewhich can be suitably used even in exposure requiring high resolution,and a pellicle using the pellicle frame.

On a semiconductor device such as an LSI and an ultra LSI and a liquidcrystal display panel, a pattern can be formed by irradiating a light toa semiconductor wafer or an original plate for liquid crystal (patternformation by lithography). Here, in the case of using an exposure masterplate to which dust adheres, since the dust absorbs and/or inverts thelight, the pattern is not transferred satisfactorily (for example,deformation of the pattern or ambiguity of the edge). As a result, thequality and appearance of the semiconductor device and the liquidcrystal display panel are impaired, which results in a decrease inperformance and manufacturing yield.

For this reason, the lithography process is usually performed in a cleanroom, but, since adhesion of dust to the exposure master plate cannot becompletely prevented even under such environment, usually a pellicle forprotecting from dust is provided on the surface of the exposure masterplate. Pellicle is composed of a pellicle frame and a pellicle filmstretched over the pellicle frame and is placed so as to surround apattern area formed on the surface of the exposure master plate. Whenthe focal point is set on the pattern of the exposure master plate atthe time of lithography, even if dust adheres to the pellicle film, thedust will not affect the transfer. Success

Here, with respect to the pellicle frame, for the purpose of preventingreflection of light from a light source to obtain a clear patterntransferred image, facilitating foreign matter adhesion inspection orthe like before use, and the like, it is usual that an aluminum materialis blackened after the anodizing treatment, for example, there is knowna method in which an organic dye or the like penetrates into pores ofthe anodized film to make it black.

Recently, the pattern of the LSI has been rapidly advanced to fineness,and accordingly, a wavelength of the exposure light source has beenshortened. Specifically, the wavelength has transited from g-line (436nm) and i-line (365 nm) of a mercury lamp to KrF excimer laser (248 nm),ArF excimer laser (193 nm) and the like, and thus the flatness requiredfor the exposure master plate and a silicon wafer has become moresevere.

After the exposure master plate is completed, the pellicle is affixed tothe exposure master plate for protection of the pattern from dust. Whenthe pellicle is affixed to the exposure master plate, there is a casethat the exposure master plate may be distorted and the flatness may bechanged, and there rises a problem that defocusing may occur due to thedecrease in the flatness of the exposure master plate. When the flatnessof the exposure master plate is changed, the figure of the pattern drawnon the exposure master plate is changed, and overlay accuracy of theexposure master plate is reduced. Here, it is known that the change inthe flatness of the exposure master plate by the affix of the pellicleis greatly influenced by the deformation stress when the pellicle frameis affixed. The stress is expressed by a product of a bulk modulus and arigidity ratio, and in order to reduce the stress, it is effective toreduce the flatness of the pellicle frame to reduce the bulk modulus.The rigidity ratio is expressed by a product of a moment of inertia ofarea and a Young's modulus, and by lowering the height of the pellicleframe and decreasing the moment of inertia of area, or by decreasing theYoung's modulus of the pellicle frame, it is effective to make therigidity ratio smaller.

On the other hand, for example, in Patent Literature 1 (JP 2011-7934 A),there is disclosed a pellicle frame that a cross section of the pellicleframe bar has a shape having a quadrangular depression on both sides ofa basic quadrilateral in which the upper side and the lower side areparallel.

In the pellicle frame described in the above Patent Literature 1, it ispossible to form a pellicle frame having a small deformation stress byreducing the cross-sectional area of the pellicle frame compared to thebasic quadrilateral. Therefore, even if the pellicle is affixed to theexposure master plate, the deformation of the exposure master platecaused by the deformation of the pellicle frame can be reduced as muchas possible.

CITATION LIST Patent Literature

Patent Literature 1: JP 2011-7934 A

SUMMARY OF INVENTION Technical Problem

However, in the pellicle frame described in Patent Literature 1, it isnecessary to process for forming the depression on the quadrilateral,which makes not only complicating the manufacturing process, but alsobeing disadvantageous in terms of cost. In addition, the effect ofinhibiting the distortion of the photomask by the pellicle frame isstill insufficient.

Considering the above problems in the prior arts, an object of thepresent invention is to provide a pellicle frame which can effectivelyinhibit distortion of the photomask caused by mounting the pellicle, andwhich does not have a complex shape, and a pellicle which uses saidpellicle frame are provided.

Another object of the present invention is to provide a manufacturingmethod of a blackened pellicle frame is also provided which can reducethe defect of the surface flickering under concentrated light and whichfacilitates inspection of the foreign matter adhesion prior to use.

Solution to Problem

As a result of extensive study with respect to the materials and thelike for a pellicle frame in order to achieve the above object, thepresent inventors have found that utilization of an aluminum-calcium(Al—Ca) alloy and the like is extremely effective in inhibiting thedeformation of the exposure master plate, the present invention has beencompleted.

Namely, the present invention is to provide a pellicle frame with ananodized film on a surface of an aluminum alloy frame, characterized inthat:

the aluminum alloy frame comprises an aluminum alloy which contains Ca:5.0 to 10.0% by mass with the remainder aluminum and unavoidableimpurities are contained, and has an area (volume) ratio of an Al₄Caphase, which is a dispersed phase, is greater than or equal to 25%, anda crystal structure of a part of the Al₄Ca phase is monoclinic; wherein

the Al₄Ca phase dispersed in the anodized film is anodized, and

the anodized film is stained with a black dye.

In order to inhibit the deformation of the exposure master plate, apellicle frame is required to have a low Young's modulus. By using anAl—Ca alloy having a Young's modulus lower than a general aluminumalloy, it is possible to obtain both of a low Young's modulus and amechanical strength required for the pellicle frame. That is, by usingan Al—Ca alloy having a low Young's modulus as the material of thepellicle frame, the deformation of the exposure master plate can beeffectively inhibited even if the pellicle frame does not have acomplicated shape. Though such materials having a low Young's modulusinclude magnesium, synthetic resins, and the like, from the viewpointsof material availability and versatility, it is preferable to use Al—Caalloy which is an aluminum alloy.

The Al—Ca alloy is not particularly limited as long as the effect of thepresent invention is not impaired, and various conventionally knownAl—Ca alloys can be used, but it is necessary that the alloy has Ca: 5.0to 10.0% by mass with the remainder aluminum and unavoidable impurities,the area (volume) ratio of the Al₄Ca phase which is the dispersed phaseis greater than or equal to 25%, and the crystal structure of a part ofthe Al₄Ca phase is formed from an aluminum alloy which is monoclinic. Inthe present invention, the area (volume) ratio of the Al₄Ca phase can beeasily measured by image analysis of the cross-sectional observationimage by an optical microscope or a scanning electron microscope (SEM),for example.

By adding Ca, Al₄Ca can be prepared, and the effect of lowering theYoung's modulus of the aluminum alloy can be achieved. The effectbecomes remarkable when the content of Ca is greater than or equal to5.0%. Conversely, when added in excess of 10.0%, the castabilitydecreases, particularly casting by continuous casting such as DC castingbecomes difficult, and thus it is necessary to manufacture by a methodwith high production cost such as a powder metallurgy method. In thecase of manufacturing by a powder metallurgy method, oxides formed onthe surface of the alloy powder may get mixed in the product, which maylower the yield strength.

The crystal structure of the Al₄Ca phase used as the disperse phase isbasically tetragonal. However, as the present inventors' extensivestudy, it was found that when the Al₄Ca phase has monoclinic crystalstructure, the yield strength is not so decreased but the Young'smodulus decreased greatly. Here, by setting the volume ratio of theAl₄Ca phase to greater than or equal to 25%, the Young's modulus can begreatly decreased while maintaining the yield strength as it is. Thepresence or absence of the Al₄Ca phase and the crystal structure can beevaluated by, for example, an X-ray diffraction measurement method.

In the pellicle frame of the present invention, it is preferable that aV content and a Fe content of the aluminum alloy are 0.0001 to 0.005% bymass and 0.05 to 1.0% by mass, respectively. When V is present in theAl—Ca alloy in an amount of around 1%, a compound having a size of 30 μmor more is formed with Ca, Ti, Al or the like, and white spot defectssometimes become apparent after the anodizing treatment. On the otherhand, by inhibiting the V content within the range of 0.0001 to 0.005%by mass, it is possible to inhibit the white spot defects.

Also, when casting the Al—Ca alloy, there is a case that a fine eutecticstructure may be formed in the vicinity of the a phase (Al phase), andafter subjecting the Al—Ca alloy having the fine eutectic structure toplastic working, when applying the anodizing treatment, the portioncorresponding to the fine eutectic texture is emphasized in black due tothe difference in the structure, which results in a black defect. On theother hand, the Al—Ca alloy to which 0.05 to 1.0% by mass of Fe is addedis made coarse and has a homogeneous cast structure to make the fineeutectic is blurred, so that it can be prevented from becoming blackdefects.

Further, in the pellicle frame of the present invention, the averagecrystal grain size of the Al₄Ca phase is preferably smaller than orequal to 1.5 μm. By dispersing finer Al₄Ca phases, it is possible topromote the blackening after the anodizing treatment.

Distortion of the exposure master plate by affixing the pellicle to theexposure master plate is greatly affected by distortion of the pellicleframe. At the time of affixing, the pellicle frame deforms, and theexposure master plate is deformed by the deformation stress caused byget back to the original. Since the deformation stress depends on theYoung's modulus of the material constituting the pellicle frame and thedeformation amount thereof, by using an Al—Ca alloy having a low Young'smodulus, when the pellicle is affixed to the exposure master plate, itis possible to realize a pellicle frame having a small deformationstress.

In the pellicle frame of the present invention, it is preferable thatthe Al—Ca alloy is processed as a hot extruded material. Since the hotextruded Al—Ca alloy material has both the low Young's modulus and themechanical strength required for the pellicle frame, it can be suitablyused as a material of a pellicle frame. Furthermore, it is also possibleto increase the mechanical strength by subjecting to cold rolling afterthe hot extrusion.

In the pellicle frame of the present invention, it is preferable thatthe Al—Ca alloy is processed as a hot rolled material. Since the hotrolled Al—Ca alloy material has both the low Young's modulus and themechanical strength required for the pellicle frame, it can be suitablyused as a material of a pellicle frame. Furthermore, it is also possibleto increase the mechanical strength by subjecting it to cold rollingafter hot extrusion. The Al—Ca alloy powder material produced by anatomization method is sandwiched between two pieces of aluminum platesserving as skin members, subjected to hot rolling, and the resultantplate material is framed by mechanical work, whereby the hot rolledmaterial can be obtained.

Further, in the pellicle frame of the present invention, it ispreferable that the Al—Ca alloy is produced by a die casting method.Since the Al—Ca alloy material produced by the die casting has both thelow Young's modulus and the mechanical strength required for thepellicle frame, it can be suitably used as a material of a pellicleframe. Further, by manufacturing an Al—Ca alloy material for a pellicleframe by the die casting, mechanical works can be reduced, and the Al—Caalloy material having a low Young's modulus and a high strength can beefficiently obtained.

A powder sintered material can also be used for the pellicle frame ofthe present invention. The powder sintered material has proper voids inthe material, and the Young's modulus can be efficiently lowered by thevoids. Since the Young's modulus and the mechanical strength can becontrolled by the porosity or the like, it is possible to achieve boththe mechanical strength required for the pellicle frame and the lowYoung's modulus. A powder sintered material can be observed with across-sectional SEM (Scanning Electron Microscope).

Further, in the pellicle frame of the present invention, for example, itis possible to use a powder sintered material obtained by processing apowder sintered body as the hot extruded material. When processing inhot processing methods such as hot forging and hot extrusion of an Al—Caalloy powder material, there happens defects such as blister in somecases, but it is possible to inhibit occurrence of the defect byhot-extruding the Al—Ca alloy powder sintered body.

In the pellicle frame of the present invention, the Ca content of theAl—Ca alloy is preferably 5 to 10% by mass. When the Ca content isgreater than or equal to 5% by mass, an Al₄Ca phase is properly formed,and an effect of reducing the Young's modulus is obtained. In addition,when the Ca content is smaller than or equal to 10% by mass, the amountof Al₄Ca phase does not become too large, and the material can beprotected from becoming brittle, which results in endow with asufficient strength.

Also, in order to inhibit a haze at the time of using the pellicle, itis preferable to anodize with an alkaline aqueous solution containingtartaric acid. Though the Al₄Ca phase exists in the Al—Ca alloy in thedispersed manner, it is preferable that the Al₄Ca phase in the anodizedfilm is anodized. By adding tartaric acid, it is possible to anodize Alphase and Al₄Ca phase. Here, when removing the Al₄Ca phase by anodizing,voids or the like are formed, and it is possible to proceed theblackening. Furthermore, after the anodizing treatment, by subjecting toa dyeing treatment with a black dye, it is possible to make a blackpellicle frame having a lightness index L* value of smaller than orequal to 30 based on a Hunter's color difference formula, which caninhibit the white spots due to crystallization. In addition, it is easyto detect dust and the like. The preferable L* value is greater than orequal to 10 and smaller than or equal to 30. Further, in order toprotect the surface, a resin film may be further provided on theanodized film. The kind of resin may not be particularly limited. Theresin film can be formed by coating the resin on the anodized film.

Further, the present invention relates to a method for manufacturing apellicle frame, comprising:

a first step for obtaining an aluminum alloy plastic worked bysubjecting an aluminum alloy ingot which contains 5.0 to 10.0% by massof Ca with the remainder aluminum and inevitable impurities, and has avolume ratio of an Al₄Ca phase which is a dispersed phase of 25% or moreto a plastic working,

a second step for subjecting the aluminum alloy plastic worked to a heattreatment in a temperature range of 100 to 300° C., and

a third step for subjecting the heat-treated aluminum alloy plasticworked to an anodizing treatment with an alkaline electrolytic solutioncontaining tartaric acid as an electrolyte.

A Young's modulus of the Al—Ca alloy varies depending on the amount ofthe Al₄Ca phase and the crystal structure. Therefore, even if the amountof the Al₄Ca phase is the same, the crystal structure is changed by theplastic working in the first step, and the Young's modulus may beincreased in some cases. On the other hand, by subjecting to the heattreatment (annealing treatment) in the temperature range of 100 to 300°C. after the plastic working, it is possible to return the crystalstructure of the Al₄Ca phase to the state before the plastic working,and further to lower the Young's modulus. Therefore, even if the secondstep and the third step are exchanged, the same effect can be obtained,but in that case, it is necessary to consider the damage (crack etc.) tothe film by heat treatment.

In the manufacturing method of the pellicle frame of the presentinvention, it is preferable that the V content and the Fe content of thealuminum alloy ingot are set to 0.0001 to 0.005% by mass and 0.05 to1.0% by mass, respectively.

By setting the V content of the aluminum alloy ingot to 0.0001 to 0.005%by mass, it is possible to inhibit the formation of a compound ofgreater than or equal to 30 μm by reaction with V and Ca, Ti, Al and thelike. As a result, the formation of the white spot defects can beinhibited after the anodization treatment (third step).

Further, by setting the Fe content to 0.05 to 1.0% by mass, the caststructure of the Al—Ca alloy can be made coarse and uniform. As aresult, the fine eutectic structure emphasized after the anodizationtreatment (third step) can be blurred, and the formation of the blackdefects can be inhibited.

In the manufacturing method of the pellicle frame of the presentinvention, it is preferable to achieve the heat treatment to maintainthe aluminum alloy ingot at a temperature of higher than or equal to400° C. before the first step. By holding (homogenizing treatment) at atemperature of higher than or equal to 400° C. prior to the plasticworking, the eutectic structure can be made coarse and uniform. As aresult, as mentioned above, the fine eutectic structure can be blurred,and the formation of the black spot defects can be inhibited.

Further, in the method for manufacturing the pellicle frame of thepresent invention, by achieving an anodization treatment (third step) onthe aluminum alloy plastic worked which has been subjected to the heattreatment with an alkaline electrolytic solution containing tartaricacid as an electrolyte, it is possible to anodize the Al phase and theAl₄Ca phase. Here, the voids and the like are formed by removing theAl₄Ca phase by anodization, and blackening can proceed.

Furthermore, after the anodization treatment (third step), by subjectingthe dyeing treatment with a black dye, the L* value of the pellicleframe can be reduced to smaller than or equal to 30. The preferable L*value is greater than or equal to 10 and smaller than or equal to 30.

The present invention also provides

a pellicle having the pellicle frame of the present invention and

a pellicle film supported by the pellicle frame.

Since the pellicle frame of the present invention achieves both themechanical strength and the low Young's modulus required for thepellicle frame, the pellicle of the present invention can maintainextremely good flatness.

Effects of the Invention

According to the present invention, it is possible to provide a pellicleframe which can effectively inhibit distortion of the photomask causedby mounting the pellicle, and which does not have a complex shape.Further, according to the present invention, it is possible to provide apellicle having extremely good flatness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing one example of thepellicle of the present invention configured using the pellicle frame ofthe present invention.

FIG. 2 is a schematic plan view showing one example of the pellicleframe of the present invention.

FIG. 3 is an X-ray diffraction pattern of the aluminum alloy plasticworked obtained in Example.

FIG. 4 is an optical microscopic photograph of the cross section of thepellicle frame of Example.

EMBODIMENTS FOR ACHIEVING THE INVENTION

Hereinafter, representative embodiments of the pellicle frame and thepellicle of the present invention will be described in detail withreference to the drawings, but the present invention is not limited toonly these examples. In the following description, the same orequivalent parts are denoted by the same numerals, and there is a casethat redundant explanation may be omitted. In addition, since thedrawings are for conceptually explaining the present invention,dimensions of the respective constituent elements expressed and ratiosthereof may be different from actual ones.

1. Pellicle Frame and Pellicle

The pellicle frame of the present invention is a pellicle framecharacterized by being made of an Al—Ca alloy, and by stretching andaffixing a pellicle film on one end surface of the pellicle frame via anadhesive for pellicle film, it is possible to use as a pellicle framefor lithography.

A schematic sectional view of one example of the pellicle of the presentinvention constituted by using the pellicle frame of the presentinvention and a schematic plan view of the pellicle frame of the presentinvention are shown in FIG. 1 and FIG. 2, respectively. The pellicle 1is obtained by stretching and affixing a pellicle film 6 on the upperend surface of a pellicle frame 2 via an adhesive layer 4 for affixingthe pellicle film. When using the pellicle 1, a pressure sensitiveadhesive layer 10 for adhering the pellicle 1 to the exposure masterplate (mask or reticle) 8 is formed on the lower end surface of thepellicle frame 2, and a liner (not shown) is peelably adhered to thelower end surface of the pressure sensitive adhesive layer 10.

It is preferable that the pellicle frame 2 is made of an Al—Ca alloy,and the Al—Ca alloy is processed as a hot extruded material or a hotrolled material, or manufactured by a die casting method. By using thesemethods, it is possible to efficiently obtain an Al—Ca alloy having boththe low Young's modulus and the mechanical strength required for thepellicle frame. The process steps of the hot extrusion, hot rolling, anddie casting are not particularly limited as long as the effects of thepresent invention are not impaired, and various conventionally knownmethods can be used. Furthermore, by achieving the cold rolling afterthe hot extrusion, the mechanical strength can also be increased.

A powder sintered material can also be used for the above Al—Ca alloy.In order to improve the flatness of the exposure master plate (mask orreticle) 8 after adhering the pellicle 1, the pellicle frame 2 having alow Young's modulus is required. Comparing with general aluminum alloys,the Al—Ca alloy has a low Young's modulus, and in addition thereto, aYoung's modulus thereof can be set to a lower value by using the powdersintered material having voids.

The Al—Ca alloy is not particularly limited as long as the effects ofthe present invention are not impaired, and various conventionally knownAl—Ca alloys can be used, but, according to the crystal structure, shapecontrol, and the like of the Al₄Ca crystal, it is preferable to use anAl—Ca alloy that achieves both the low Young's modulus and the excellentrolling processability.

Since the powder sintered material has proper voids in the material, bycontrolling the ratio, size, dispersion state, and the like of thevoids, it is possible to balance both the mechanical strength requiredfor the pellicle frame 2 and the low Young's modulus. Examples of thematerials having a low Young's modulus include magnesium, syntheticresins, and the like, but from the viewpoints of material availabilityand versatility, it is preferable to use an Al—Ca alloy which is analuminum alloy.

As described above, the distortion of the exposure master plate (mask orreticle) 8 by affixing the pellicle 1 to the exposure master plate (maskor reticle) 8 is greatly affected by the distortion of the pellicleframe 2. At the time of the affixing, the pellicle frame 2 is deformed,and the exposure master plate (mask or reticle) 8 is deformed by thedeformation stress that tries to back to the original shape. Since thedeformation stress depends on the Young's modulus of the materialconstituting the pellicle frame 2 and the deformation amount thereof, byusing an Al—Ca alloy having a low Young's modulus (in particular, thepowder sintered material), it is possible to realize the pellicle frame2 having a small deformation stress when affixes the pellicle 1 to theexposure master plate (mask or reticle) 8.

As the material of the pellicle frame 2, it is preferable to use amaterial which is obtained by processing the powder sintered body of theAl—Ca alloy as a hot extruded material. When achieving the hotprocessing such as hot forging or hot extrusion of the Al—Ca alloypowder material, though defects such as blister may be generated in somecases, by hot-extruding the Al—Ca alloy powder sintered body, it ispossible to obtain a material in which occurrence of the defect isinhibited.

The method for preparing the hot extruded Al—Ca alloy powder materialused as the material of the pellicle frame 2 is not particularlylimited, but it is preferably prepared by molding a raw material powderthrough a CIP method or the like (for example, Al—Ca alloy powderprepared by a quenched solidification method such as an atomizingmethod, a mechanical alloying method, or the like), heating andsintering the Al—Ca alloy powder molded body in vacuum or in an inertgas atmosphere, cooling the sintered body in vacuum or in an inert gasatmosphere, and hot-extruding the obtained sintered body. Here, theporosity of the hot extruded Al—Ca alloy powder material can beappropriately controlled depending on the compacting condition, thesintering condition, the extrusion condition, the oxidation state of thesurface of the raw powder material, and the like.

Further, in the material of the pellicle frame 2, it is preferable thatthe Ca content of the Al—Ca alloy is 5 to 10% by mass. When the Cacontent is greater than or equal to 5% by mass, an Al₄Ca phase isproperly formed, and the Young's modulus can be effectively reduced. Inaddition, when the Ca content is smaller than or equal to 10% by mass,the amount of Al₄Ca phase does not become too large, and it is possibleto inhibit that the material becomes brittle, which results in givingthe sufficient strength.

In order to form a uniform anodized film, an etching treatment using anacid or an alkali may be achieved as a pretreatment, and in order tofacilitate detection when dust or the like adheres to the obtained framebody, a blast treatment or the like may be applied. On the other hand,in order to increase the degree of cleaning, cleaning treatment such aspure water cleaning, hot water cleaning, ultrasonic cleaning or the likemay be achieved after the anodizing treatment, the coloring treatmentand the sealing treatment.

The shape of the pellicle frame 2 is not particularly limited as long asthe effects of the present invention are not impaired and can be variousconventionally known shapes according to the shape of the exposuremaster plate (mask or reticle) 8, but, in general, the plane shape ofthe pellicle frame 2 is a ring shape, a rectangular shape or a squareshape and has a size and shape to cover the circuit pattern portionprovided on the exposure master plate (mask or reticle) 8. In addition,the pellicle frame 2 may be provided with an air pressure adjustmentvent (not shown), a dust removal filter (not shown) for the vent, jigholes (not shown), and the like.

The height (thickness) of the pellicle frame 2 is preferably 1 to 10 mm,more preferably 2 to 7 mm, and most preferably 3 to 6 mm. By setting theheight (thickness) of the pellicle frame 2 to these values, thedeformation of the pellicle frame 2 can be inhibited, and good handlingproperty can be ensured.

The cross-sectional shape of the pellicle frame 2 is not particularlylimited as long as the effects of the present invention are not impairedand can be various conventionally known shapes, but it is preferablethat the cross-sectional shape is a quadrilateral in which the upperside and the lower side are parallel. There are required a width foraffixing the pellicle film 6 is required on the upper side of thepellicle frame 2, and a width for adhering to the exposure master plate8 by providing the adhesive layer 10 for pressure sensitive adhesion onthe lower side. For this reason, the width of the upper side and thelower side of the pellicle frame 2 is preferably about 1 to 3 mm.

The flatness of the pellicle frame 2 is preferably smaller than or equalto 20 μm, more preferably smaller than or equal to 10 μm. By improvingthe flatness of the pellicle frame 2, it is possible to reduce thedeformation amount of the pellicle frame 2 when the pellicle 1 isattached to the exposure master plate (mask or reticle) 8. The flatnessof the pellicle frame 2 is calculated by calculating a virtual plane bymeasuring the height at a total of 8 points including 4 corners of thepellicle frame 2 and 4 central points of the four sides, and thencalculating from the difference obtained by subtracting the lowest pointfrom the highest point among the distances of each point.

2. Method for Manufacturing Pellicle Frame

The method for manufacturing a pellicle frame of the present inventionis a method for manufacturing a pellicle frame, comprising a first stepfor obtaining an aluminum alloy plastic worked (aluminum alloy to beplastic-worked) by subjecting an aluminum alloy ingot which contains 5.0to 10.0% by mass of Ca with the remainder aluminum and inevitableimpurities, and has a volume ratio of an Al₄Ca phase which is adispersed phase of 25% or more to a plastic working, a second step forsubjecting the aluminum alloy plastic worked to a heat treatment in atemperature range of 100 to 300° C., and a third step for subjecting theheat-treated aluminum alloy plastic worked to an anodizing treatmentwith an alkaline electrolytic solution containing tartaric acid as anelectrolyte.

The Young's modulus of the Al—Ca alloy varies depending on the amount ofthe Al₄Ca phase and the crystal structure. Therefore, even if the amountof the Al₄Ca phase is the same, the crystal structure is changed by theplastic working in the first step, and the Young's modulus may beincreased in some cases. On the other hand, by achieving a heattreatment (annealing treatment) in the temperature range of 100 to 300°C. after the plastic working, it is possible to return the crystalstructure of the Al₄Ca phase to the state before the plastic working andto lower the Young's modulus.

Further, by setting the V content of the aluminum alloy ingot to 0.0001to 0.005% by mass, it is possible to inhibit the formation of a compoundof 30 μm or more by reaction with V and Ca, Ti, Al, or the like. As aresult, formation of the white spot defects after the anodizingtreatment (third step) can be inhibited.

Furthermore, by setting the Fe content to 0.05 to 1.0% by mass, it ispossible to make the cast structure of the Al—Ca alloy coarse anduniform. As a result, the fine eutectic structure emphasized after theanodizing treatment (third step) can be blurred, and the formation ofthe black defects can be inhibited.

Further, before the first step, it is preferable to subject the aluminumalloy ingot to a heat treatment at a temperature of higher than or equalto 400° C. By holding at a temperature of higher than or equal to 400°C. (homogenizing treatment) prior to plastic working, the eutecticstructure can be made coarse and uniform. As a result, as describedabove, the fine eutectic structure can be blurred, and the formation ofthe black spot defects can be inhibited.

In addition, it is possible to anodize the aluminum phase and the Al₄Caphase by applying the anodizing treatment (third step) with an alkalineelectrolytic solution containing tartaric acid as an electrolyte to theheat-treated aluminum alloy plastic worked.

Furthermore, by subjecting the dyeing treatment with a black dye afterthe anodizing treatment (third step), the L* value of the pellicle framecan be reduced to smaller than or equal to 30. The preferable L* valueis greater than or equal to 10 or more and smaller than or equal to 30.

The representative embodiments of the present invention have beendescribed above, but the present invention is not limited only to theseembodiments, and various design changes are possible, and all suchdesign changes are included in the technical scope of the presentinvention.

EXAMPLES Example

An aluminum alloy having the composition (% by mass) shown in Sample 1of Table 1 was cast into an ingot of φ8 inches (billet) by a DC castingmethod and homogenized at 550° C. for 4 hours, and then, plastic-workedat an extrusion temperature of 500° C. to obtain a plate having a widthof 180 mm×a thickness of 8 mm.

Thereafter, after cold rolling to a thickness of 3.5 mm, a heattreatment was carried out to hold at 200° C. for 4 hours to obtain apresent aluminum alloy plastic worked. This was machined to produce analuminum alloy frame in the shape of frame having an external size of149 mm×122 mm×a thickness 3 mm. After subjecting the obtained aluminumalloy frame material to a shot blasting treatment by using stainlesssteel grains having an average grain size of about 100 μm, theblast-treated aluminum alloy frame material was subjected to theanodizing treatment by using an alkaline aqueous solution (pH=13.0) asan electrolytic solution in which 53 g/L of sodium tartrate dihydrate(Na₂C₄H₄Os₂H₂O) and 4 g/L of sodium hydroxide were dissolved, at a bathtemperature of 5° C. under a constant voltage electrolysis of anelectrolytic voltage of 40 V for 20 minutes. Then, after washing withpure water, by measuring a thickness if the anodized film formed on thesurface of the aluminum alloy frame material with an eddy current typefilm thickness meter (available from Fischer Instruments Co., Ltd.), thethickness was 6.6 μm.

Subsequently, a dyeing treatment was achieved by placing the aluminumalloy frame material which was subjected to the anodizing treatment inan aqueous solution containing an organic dye (TAC 411 available fromOkuno Pharmaceutical Co., Ltd.) at a concentration of 10 g/L for 10minutes at a temperature of 55° C. After the dyeing treatment, thedye-treated aluminum alloy frame material was placed in a steam sealingapparatus and was subjected to a sealing treatment for 30 minutes whilegenerating steam at a relative humidity of 100% (R.H.), 2.0 kg/cm²G at atemperature of 130° C. to obtain a test pellicle frame according to theexample.

FIG. 3 shows the X-ray diffraction pattern of the present aluminum alloyplastic worked. In the X-ray diffraction measurement, a specimen of 20mm×20 mm was cut out from the plate-like present aluminum alloy plasticworked, the surface layer portion was scraped by about 500 μm, and thena θ-2θ measurement was carried out with respect to the region by a Cu-Kαbeam source. From the peak position of the Al₄Ca phase in FIG. 3, it canbe seen that the tetragonal Al₄Ca phase and the monoclinic Al₄Ca phaseare mixed in the present aluminum alloy plastic worked.

The result of the structure observation (optical microscopic photograph)on the cross section of the present pellicle frame is shown in FIG. 4.The black region was the Al₄Ca phase, and the area (volume) ratio of theAl₄Ca phase was measured by an image analysis and was 36.8%.

The present pellicle frame of the example was cut into a test piece, anda tensile strength was measured by a tensile test, and, a yield strengthand a Young's modulus were measured. The obtained results are shown inTable 2. In addition, the present pellicle frame was cut and aligned toform a 30×30 mm surface, and the lightness index L* value was measuredusing a CR-400 available from KONICA MINOLTA CORPORATION using aHunter's color difference formula of the present pellicle frame. Theresults are shown in Table 2.

Comparative Example 1

A comparative pellicle frame 1 having an anodized film having a filmthickness of 7.1 μm was prepared in the same manner as in Example 1except that the composition (% by mass) shown in Sample 2 in Table 1 wasused. A tensile strength, a yield strength, a Young's modulus and an L*value of the comparative pellicle frame 1 were measured in the samemanner as in the above example. The obtained results are shown in Table2.

Further, in the same manner as in the above example, the structureobservation on the cross section of the comparative pellicle frame 1 wascarried out, and an area (volume) rate of the Al₄Ca phase was measuredby an image analysis and found to be 15.9%.

Comparative Example 2

A comparative pellicle frame 2 having an anodized film with a filmthickness of 6.6 μm was prepared by anodizing in the same manner as inthe above example except that 8 g/L of sodium hydroxide was used as anelectrolytic solution for anodizing treatment, and steam sealing wasconducted after the anodizing without the dyeing treatment. A tensilestrength, a yield strength, a Young's modulus and an L* value of thecomparative pellicle frame 1 were measured in the same manner as in theabove example. The obtained results are shown in Table 2.

TABLE 1 Ca V Fe Al Sample 1 7.44 0.001 0.05 Bal. Sample 2 2.53 0.0010.06 Bal.

TABLE 2 Tensile Yield Young's strength strength modulus (MPa) (MPa)(GPa) L* value Example 224 171 50.2 28.4 Com. Example 1 185 161 62.527.6 Com. Example 2 224 171 50.2 40.6

The Young's modulus of the pellicle frame produced from the 7.44% bymass Ca alloy in the example is 50.2 GPa, which is much smaller thanthat of the Comparative example 1 (62.5 GPa). Here, the Young's modulusof Comparative Example 2 which is not dyed also shows a small value of50.2 GPa, but the L* value is as large as 40.6.

EXPLANATION OF SYMBOLS

-   1: Pellicle-   2: Pellicle frame-   4: Adhesive layer for affixing the pellicle film-   6: Pellicle film-   8: Exposure master plate (mask or reticle)-   10: Pressure sensitive adhesion layer

1. A pellicle frame with an anodized film on a surface of an aluminumalloy frame, characterized in that: the aluminum alloy frame comprisesan aluminum alloy which contains Ca: 5.0 to 10.0% by mass with theremainder aluminum and unavoidable impurities are contained, and has anarea (volume) ratio of an Al₄Ca phase, which is a dispersed phase, isgreater than or equal to 25%, and a crystal structure of a part of theAl₄Ca phase is monoclinic; wherein the Al₄Ca phase dispersed in theanodized film is anodized, and the anodized film is stained with a blackdye.
 2. The pellicle frame according to claim 1, wherein a V content anda Fe content of the aluminum alloy are 0.0001 to 0.005% by mass and 0.05to 1.0% by mass, respectively.
 3. The pellicle frame according to claim1, wherein an average crystal grain size of the Al₄Ca phase is 1.5 μm orless.
 4. The pellicle frame according to claim 1, further comprising aresin film on the anodized film.
 5. A method for manufacturing apellicle frame, comprising: a first step for obtaining an aluminum alloyplastic worked by subjecting an aluminum alloy ingot which contains 5.0to 10.0% by mass of Ca with the remainder aluminum and inevitableimpurities, and has a volume ratio of an Al₄Ca phase which is adispersed phase of 25% or more to a plastic working, a second step forsubjecting the aluminum alloy plastic worked to a heat treatment in atemperature range of 100 to 300° C., and a third step for subjecting theheat-treated aluminum alloy plastic worked to an anodizing treatmentwith an alkaline electrolytic solution containing tartaric acid as anelectrolyte.
 6. The method for manufacturing a pellicle frame accordingto claim 5, wherein, before the first step, the aluminum alloy ingot issubjected to a heat treatment where the ingot is maintained at atemperature of 400° C. or more.
 7. A pellicle comprising the pellicleframe according to claim 1 and a pellicle film supported by the pellicleframe.